Processes for producing 5-fluorobenzoic acids and their intermediates

Abstract

A process for producing a 5-fluorobenzoic acid of the formula (V), which comprises trichloromethylating a fluorobenzene of the formula (I) to obtain a 5-fluorobenzotrichloride of the formula (II), then reacting it with aqueous ammonia to obtain a 5-fluorobenzonitrile of the formula (III), reacting it with a fluorinating agent to obtain a 5-fluorobenzonitrile of the formula (IV) and hydrolyzing it: ##STR1## wherein each of X 1 , X 3 , Y 1 and Y 3 is a halogen atom, and each of X 2 and Y 2 is hydrogen or a halogen atom.

We claim: 
     
       1. A process for producing a 5-fluorobenzoic acid of the formula (V), which comprises trichloromethylating a fluorobenzene of the formula (I) to obtain a 5-fluorobenzotrichloride of the formula (II), then reacting it with aqueous ammonia to obtain a 5-fluorobenzonitrile of the formula (III), reacting it with a fluorinating agent to obtain a 5-fluorobenzonitrile of the formula (IV) and hydrolyzing it: ##STR4## wherein each of X 1 , X 3 , Y 1  and Y 3  is a halogen atom, and each of X 2  and Y 2  is hydrogen or a halogen atom, with the proviso that at least one of X 1 , X 2  and X 3  is a halogen atom other than fluorine, wherein said step of reacting the compound of formula (III) with a fluorinating agent converts at least one of said halogen atom other than fluorine to fluorine at the corresponding ring position of Y 1 , Y 2  and Y 3 . 
     
     
       2. A process for producing a 5-fluorobenzoic acid of the formula (VI), which comprises reacting a fluorobenzene of the formula (I) with carbon tetrachloride in the presence of a Lewis acid catalyst to obtain a 5-fluorobenzotrichloride of the formula (II), and hydrolyzing it: ##STR5## wherein each of X 1  and X 3  is a halogen atom, and X 2  is hydrogen or a halogen atom.